This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the presently described embodiments. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present embodiments. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
In order to meet consumer and industrial demand for natural resources, companies often invest significant amounts of time and money in finding and extracting oil, natural gas, and other subterranean resources from the earth. Particularly, once a desired subterranean resource such as oil or natural gas is discovered, drilling and production systems are often employed to access and extract the resource. These systems may be located onshore or offshore depending on the location of a desired resource. Further, such systems generally include a wellhead assembly through which the resource is accessed or extracted. These wellhead assemblies may include a wide variety of components, such as various casings, valves, fluid conduits, and the like, that control drilling or extraction operations. Subsea wellhead assemblies typically include control pods that operate hydraulic components and manage flow through the assemblies.
This invention relates to a closed-loop solenoid pressure supply system for operating subsea hydraulically-actuatable devices such as valves, blowout preventers and hydraulically actuated wellhead connectors. Such devices require pressurized hydraulic fluid, typically operated up to 5,000 psi, for their operation. The disclosed closed-loop solenoid pressure supply system is used in the control of the flow of such pressurized hydraulic fluid.
Subsea hydraulic control systems typically consist of a group of hydraulic fluid accumulators, a control unit for operating solenoid valves which control hydraulic fluid supply, and high pressure lines or hoses which carry the hydraulic control fluid from the accumulator bottles to the control unit and on to the component to be operated, e.g., valve, blowout preventer, wellhead connector, and the like. Pressurized hydraulic control fluid is stored in the accumulator bottles at a desired operating pressure, e.g., 1500, 3000 psi, 4,500 psi. This hydraulic fluid is used throughout the subsea system. Typically, hydraulic fluid used in a control system is a mixture of mostly water and a concentrate fluid that provides lubricity and corrosion protection for proper operation of the valves in the system. Frequently, the control fluid is not properly maintained and will become contaminated due to bacteria growing in the system or lack of maintenance. It is widely accepted in the industry that fluid contamination is a wide spread problem that can lead to considerable non-productive time and, accordingly, lost revenue.
Solenoid valves disposed in the control pod are particularly susceptible to hydraulic fluid contamination. Because existing subsea systems use the same hydraulic fluid throughout the system, contamination of the hydraulic fluid exposes all components, including solenoid valves, to the contamination. Accordingly, it is desirable to have a control system with reduced contamination of solenoid valves disposed therein. The present invention relates to a closed-loop solenoid valve pressure supply system, wherein the solenoid valves have their own dedicated hydraulic fluid supply separate from the hydraulic fluid used for the rest of the system, i.e., the main hydraulic fluid supply. Because the solenoid valves have their own dedicated fluid supply in a closed-loop system, the fluid can be a high quality fluid that will not degrade over time and can be filtered to a high degree to protect the solenoid valves. By reducing contamination and increasing fluid quality, the life of each solenoid valve can be greatly extended.
The illustrated figures are only exemplary and are not intended to assert or imply any limitation with regard to the environment, architecture, design, or process in which different embodiments may be implemented.